The present invention relates in general to a lighting apparatus and is concerned, more particularly, with a fluorescent-type lighting device. Although the apparatus disclosed herein is for use with coal mining equipment, it is understood that the principles of this invention may be applied in different fields of use.
The lighting devices that are presently employed on coal mining equipment are not satisfactory for a number of reasons. Many of these devices are not operated efficiently and there is an excess amount of electricity that is used in order to maintain even a minimum predetermined light level in the mines. Some of the prior art devices are rather crude in construction and do not provide sufficient protection for the light source. Other known devices are not easily disassembled while others require that almost the entire device be disassembled to replace the light source. One of the problems that has been encountered is that, since these units are completely sealed to prevent explosions in hazardous atmospheres, there is no convection cooling that can be used and thus the lamp, when warmed up, operates at a significantly reduced light level. Other prior devices require a relatively large area on the machine for attachment, whereas our unit uses less space and fewer of the units are needed to provide the same total light output.
Accordingly, one object of the present invention is to provide a lighting appratus of improved construction and one which overcomes the hereinbefore recited deficiencies of prior art devices.
Another object of the present invention is to provide a lighting apparatus which is more efficient in operation and can operate at higher light output levels than comparable devices. In accordance with the invention two techniques can be used. One is a heat sinking technique and the other depends on a specially designed fluorescent amalgam lamp using a mercury pressure regulating technique.
A further object of the present invention is to provide a lighting apparatus which comprises a lamp assembly which is easily removed from the lighting apparatus for the purpose of replacing the light source.
Still another object of the present invention is to provide a lighting apparatus which also includes a protective cage mounted about the light assembly for protection thereof.
A further object of the present invention is to provide a lighting apparatus that is rugged in construction, easy to maintain and is inherently safer in operation in hazardous atmospheres. In accordance with this invention the fluorescent tube is spring biased at both ends so that if the tube breaks the opposite ends of the tube will be automatically disengaged from their electrical contact points.
A further object of the invention is to provide a luminaire having a high optical efficiency partly with the use of a reflector which is built in as part of the lamp. This reflector is preferably a 135.degree. reflector.